Three-dimension (3D) multiple input multiple output (MIMO) can be implemented by using a large-scale antenna array to improve a utilization ratio of spectrum in a 5G mobile communication system. However, since a large-scale antenna array includes a large quantity of antennas and radio frequency channels, a data rate of an Interface Radio frequency (IR) interface between the active antenna array and a baseband unit (BBU) is very high. The data rate of the IR interface is also proportional to a supported bandwidth. It is difficult for a large-scale antenna array to support a large bandwidth due to limited interface data rate.
A large-scale antenna array needs to be used to implement 3D MIMO. A quantity of antennas in the large-scale antenna array is 2 to the power of N, generally at least 16, or as many as 128, 256, or more. The antennas compose a dually polarized antenna array and are arranged in M rows by P columns, where both M and P are exponents of 2. An antenna array in a vertical direction can perform beam scanning in the vertical direction, and an antenna array in a horizontal direction can perform beam scanning in the horizontal direction, to form a change in 3D beam scanning. A beam scanning range of antennas in the vertical direction (e.g., dually polarized antennas arranged in a row) is required to be narrow, whereas a beam scanning range of antennas in the horizontal direction (e.g., dually polarized antennas arranged in a column) is required to be wide. A sampling rate for a Long Term Evolution (LTE) signal with a 20 MHz bandwidth is 30.72 MSPS. For example, data of an IR interface is not compressed, and the transmission data rate of the IR interface as required for a carrier antenna (CA) is 1.2288 Gbps. Data of only eight CAs can be transmitted over an optic fiber of 10 Gbps. Taking 128 antennas as an example, 256 CAs are required to form 128 antennas of a total 40 MHz bandwidth, as a result, 32 optic fibers of 10G each are needed, and 80 optic fibers of 10G each are needed to support an 100M bandwidth, which is such a large quantity of optic fibers that may be infeasible.
Accordingly, two optic fibers of 10G each are configured for every eight antennas among existing technologies, and thus a bandwidth of only 40 MHz can be supported. It is difficult to provide a larger bandwidth, especially a bandwidth of 100 MHz required by the 5G system.
In summary, the small bandwidth of the conventional large-scale antenna array cannot meet the requirements of the future 5G system.